Airborne Gravity 2010 - Geoscience Australia

Airborne Gravity 2010
GOCE gravity gradiometry: Examples of gravity
field interpretation from the South-Central
American active continental margins
Abstract
Hans-Jürgen Götze 1 and Rezene Mahatsente 2
1 Christian-Albrechts-Universität Kiel (hajo@geophysik.uni-kiel.de)
2 Christian-Albrechts-Universität Kiel (rezene@geophysik.uni-kiel.de)
The new generation satellite-derived gravity and gradient data combined with surface observations
has the potential to extend existing interpretation in active convergent plate boundaries and could
provide opportunities to enhance understanding of structures of the crust and lithospheric mantle in
remote regions. Preliminary studies from the South-Central Chile subduction zone suggest that
satellite gravity has the resolution required to resolve lithospheric structure in active convergent plate
boundary. When combined with co-seismic high moment release predictions (seismic b-value
distributions 1 ), isostatic residual anomalies could also be used to map asperities 2 in active convergent
zone.
Introduction
Interdisciplinary interpretation is essential for any numerical modelling of structures and dynamic
processes, and for any geophysical interpretation. When considering the amount of available 'state of
the art' information contained in comprehensive databases, a combination of different geophysical
surveys employing seismology, potential fields and electromagnetic methods in conjunction with
geological and petrological interpretations could provide new insights into structures and the tectonic
evolution of the lithosphere and the crust-mantle interface.
The Earth Gravitational Models (e.g., EGM 2008; Pavlis et al., 2008) and the new-generation satellitederived
gravity and gradient data from CHAMP, GRACE and, in particular, GOCE are useful for
studies of the structure of the crust and lithospheric mantle. The advantage of these new models is
that they provide gravity information for areas previously lacking data that is continuous and consistent
across natural and artificial boundaries. The new gravity data that is being provided by the GRACE
satellite and the gradients that will be available from the GOCE mission by the end of 2010 provide
new opportunities to extend existing interpretations and derive insight into regions where little or no
surface data exists. In subduction zones, static (density) and dynamic modelling, constrained by
satellite gravity data, can be used to study asperities and the temporal variation of the gravity field in
response to fore-arc deformation.
Before the new satellite gravity and gradient data can be used for geophysical applications, new
methods of processing and interpretation must be developed and tested. In particular, the following
specific questions pertaining to geophysical applications need to be addressed:
(1) Are existing methods suitable to allow the use of combined surface and new-generation
satellite gravity and gradient data in studies of lithospheric mass distribution and transport?
(2) Is the information contained within new-generation satellite gravity data sufficient to constrain
models of lithospheric density, rigidity and viscosity?
(3) Is it possible to identify processes related to subduction zone asperities using new-generation
satellite gravity and gradient data?
1 “b” is a positive real constant used in the Gutenberg-Richter magnitude-frequency relationship that
describes the properties of the seismic medium through the relative abundance of large to smaller
shocks.
2 “Asperities” are areas on a fault that are stuck and sites where earthquakes begin.
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